U.S. patent application number 11/628100 was filed with the patent office on 2008-06-12 for micromechanical component having multiple caverns, and manufacturing method.
Invention is credited to Frank Fischer, Eckhard Graf, Hartmut Kueppers, Roland Scheuerer, Heiko Stahl.
Application Number | 20080136000 11/628100 |
Document ID | / |
Family ID | 34966723 |
Filed Date | 2008-06-12 |
United States Patent
Application |
20080136000 |
Kind Code |
A1 |
Fischer; Frank ; et
al. |
June 12, 2008 |
Micromechanical Component Having Multiple Caverns, and
Manufacturing Method
Abstract
A micromechanical component having at least two caverns is
provided, the caverns being delimited by the micromechanical
component and a cap, and the caverns having different internal
atmospheric pressures. The micromechanical component and cap are
hermetically joined to one another at a first specifiable
atmospheric pressure, then an access to at least one cavern is
produced, and subsequently the access is hermetically closed off at
a second specifiable atmospheric pressure.
Inventors: |
Fischer; Frank; (Gomaringen,
DE) ; Graf; Eckhard; (Gomaringen, DE) ; Stahl;
Heiko; (Reutlingen, DE) ; Kueppers; Hartmut;
(Reutlingen, DE) ; Scheuerer; Roland; (Reutlingen,
DE) |
Correspondence
Address: |
KENYON & KENYON LLP
ONE BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
34966723 |
Appl. No.: |
11/628100 |
Filed: |
April 28, 2005 |
PCT Filed: |
April 28, 2005 |
PCT NO: |
PCT/EP2005/051917 |
371 Date: |
September 14, 2007 |
Current U.S.
Class: |
257/682 ;
257/E21.505; 257/E23.128; 438/126 |
Current CPC
Class: |
B81B 7/0041 20130101;
B81C 2203/0145 20130101; B81B 2201/025 20130101; B81C 2201/019
20130101; B81B 7/02 20130101 |
Class at
Publication: |
257/682 ;
438/126; 257/E23.128; 257/E21.505 |
International
Class: |
H01L 23/055 20060101
H01L023/055; H01L 21/58 20060101 H01L021/58 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 4, 2004 |
DE |
10 2004 027 501.7 |
Claims
1-17. (canceled)
18. A micromechanical unit, comprising: a micromechanical
component; and at least one cap interfacing the micromechanical
component; wherein the micromechanical unit has at least two
caverns delimited by interfacing of the at least one cap and the
micromechanical component, and wherein the at least two caverns
have different internal atmospheric pressures.
19. The micromechanical unit as recited in claim 18, wherein the at
least two caverns are delimited by interfacing of one common cap
and the micromechanical component.
20. The micromechanical unit as recited in claim 18, wherein at
least one cavern has an access opening that is sealed with an
oxide.
21. The micromechanical unit as recited in claim 20, wherein the
access opening extends through a substrate of the micromechanical
component.
22. The micromechanical unit as recited in claim 18, wherein the
micromechanical unit has a buried conductor structure.
23. The micromechanical unit as recited in claim 18, further
comprising: at least one contact mechanism for electrical
contacting, wherein the at least one contact mechanism is located
at a contact region of a substrate of the micromechanical
component.
24. The micromechanical unit as recited in claim 18, wherein at
least one cavern is sealed by a peripheral hermetic material
seal.
25. The micromechanical unit as recited in claim 18, wherein the at
least two caverns are sealed by a common peripheral hermetic
material seal.
26. The micromechanical unit as recited in claim 18, wherein the at
least one cap includes a silicon substrate that is joined to a
glass layer.
27. The micromechanical unit as recited in claim 18, wherein the at
least one cap has at least one recess in order to form at least a
part of a cavern.
28. A method for manufacturing a micromechanical unit, comprising:
interfacing a micromechanical component and a cap to delimit at
least two caverns, wherein the micromechanical component and the
cap are hermetically joined to one another at a first specified
atmospheric pressure; providing an access to at least one cavern;
and hermetically sealing the access at a second specified
atmospheric pressure.
29. The method as recited in claim 28, wherein the cap includes a
silicon substrate joined a glass by anodic bonding.
30. The method as recited in claim 29, further comprising:
producing at least one recess in the glass in order to form a
cavern.
31. The method as recited in claim 28, wherein the micromechanical
component and the cap are joined to one another by anodic
bonding.
32. The method as recited in claim 28, wherein the access is
produced in a substrate of the micromechanical component.
33. The method as recited in claim 28, wherein the access is sealed
by a deposition process.
34. The method as recited in claim 28, further comprising:
providing an access to an additional cavern; and hermetically
sealing the access to the additional cavern at a third specified
atmospheric pressure.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a micromechanical
component, and a method for manufacturing a micromechanical
component.
BACKGROUND INFORMATION
[0002] It is known from the existing art that discrete sensors,
e.g., rotation-rate sensors and acceleration sensors, can be
manufactured micromechanically. It is likewise known that
rotation-rate and acceleration sensors can be integrated in a
common housing, together with one or more evaluation circuits, to
constitute a sensor system. It is furthermore known to integrate
micromechanical sensors and the associated evaluation circuit
monolithically. Published German patent document DE 101 04 868
describes the packaging of a micromechanical sensor by way of a
cap. The sensor and cap are anodically bonded, and delimit a
cavern. It is furthermore described in published German patent
document DE 102 43 014 to dispose two caverns in one
micromechanical component.
SUMMARY
[0003] The micromechanical component according to the present
invention has at least two caverns having different internal
pressures. This advantageously makes possible the integration of
multiple different micromechanical sensors, having different
internal atmospheric pressures as determined by their design, into
one common micromechanical component. In a micromechanical
acceleration sensor the internal atmospheric pressure in the cavern
is specified, for example, as 5 mbar to 1.5 bar. With this
pressure, a suitable damping for the micromechanical deflection
part of acceleration sensors can be established. For actively
oscillating sensors, e.g., for rotation-rate sensors, the internal
cavern pressure that is chosen should be very low in order to
ensure high quality for the oscillator. Internal cavern pressures
of <10.sup.-3 bar are advantageous here.
[0004] An advantageous example embodiment of the micromechanical
component provides for at least two caverns to be delimited by one
common cap. This makes possible a particularly compact construction
for the micromechanical component. The number of steps for
manufacturing such a component can moreover be reduced thereby. In
particular, these two caverns have different internal atmospheric
pressures.
[0005] It is also advantageous that at least one cavern has a
closed-off access opening. A specifiable pressure in the cavern can
easily be established by way of such an access opening.
[0006] A further advantageous example embodiment of the
micromechanical component according to the present invention
provides for the access opening to exist through a component
substrate. Here the access opening can be particularly easily
provided, and also closed off again, during sensor production.
[0007] It is also advantageous if the micromechanical component has
a buried conductor structure. Buried conductor structures make it
possible to configure the joining surface between the cap and the
micromechanical component in particularly flat, and therefore
sealed, fashion.
[0008] A particularly advantageous example embodiment of the
micromechanical component according to the present invention
provides for the component to have, at a contact region of a
component substrate, at least one means for electrical contacting,
in particular a metallization. This embodiment enables all the
contacts and unburied conductor structures of the micromechanical
component to be guided on the uncapped side of the micromechanical
component, thus advantageously making possible complete capping of
one side of the micromechanical component.
[0009] It is also advantageous that at least one cavern of the
micromechanical component is sealed by way of a peripheral hermetic
material join. The specified internal pressure in the cavern is
thereby advantageously maintained over the service life of the
micromechanical component.
[0010] It is also advantageous if several caverns are sealed by way
of a common peripheral hermetic material join. Advantageously,
regions of the micromechanical component can thus be provided with
the same pressure in the relevant caverns. It is furthermore also
possible to provide regions of differing pressure, in particular of
stepwise better vacuum.
[0011] An advantageous example embodiment of the micromechanical
component according to the present invention provides for the cap
to be made of a silicon substrate that is joined to a glass layer.
Such a cap can be particularly easily mounted with its glass layer
onto a micromechanical component made of silicon, and secured by
anodic bonding.
[0012] It is also advantageous if the cap, in particular the glass
layer, has at least one recess to form a cavern. The recess in the
cap advantageously enlarges the cavern. More space for
micromechanical functional parts therefore exists in the
cavern.
[0013] The method according to the present invention for
manufacturing a micromechanical component provides that the
micromechanical component and the cap are hermetically joined to
one another at a first specifiable atmospheric pressure, an access
to at least one cavern is then created, and then the access is
hermetically closed off at a second specifiable atmospheric
pressure. It is advantageous in this context that at least for one
cavern, the internal atmospheric pressure can be already be
specified during the process step of capping.
[0014] It is furthermore advantageous that different internal
atmospheric pressures are specifiable in the individual caverns,
with the result that, for example, different micromechanical
sensors, having different pressures as determined by their design,
can be manufactured.
[0015] It is moreover advantageous that the caverns made up of a
cap and micromechanical component can be manufactured by way of
joining processes at practically any desired process pressure,
since the internal cavern pressure is still modifiable
retrospectively by way of the access.
[0016] An advantageous example implementation of the method
according to the present invention provides for the cap to be
manufactured from a silicon substrate and a glass which are joined
to one another by anodic bonding. It is advantageous in this
context that in this easy fashion a cap can be manufactured and
joined to a micromechanical component in a further process step of
anodic bonding.
[0017] A further advantageous example implementation of the method
provides for at least one recess to be produced in the glass, in
particular by etching, in order to form a cavern. Advantageously,
this example implementation enables the manufacture of a cap that
makes possible, proceeding from a flat substrate and a flat glass,
the formation of the largest possible cavern.
[0018] It is also advantageous that the micromechanical component
and the cap are joined to one another by anodic bonding. Anodic
bonding makes possible the production of hermetic joins.
[0019] It is furthermore advantageous that the access is produced
in a component substrate of the micromechanical component. The
access is produced, in simple and economical fashion, in the same
manufacturing step in which trenches for the electrical insulation
of parts of the component are introduced into the component
substrate of the micromechanical component.
[0020] An advantageous example implementation of the method
according to the present invention provides for the access to be
closed off by way of a deposition process, e.g., a CVD method. A
deposition process of this kind allows the access to be closed off
at particularly low process pressures. This is advantageous for the
production of caverns having a low internal atmospheric
pressure.
[0021] It is additionally advantageous that the method steps of
opening the accesses and subsequently closing them off at a
specifiable atmospheric pressure can be performed several times
successively. It is possible as a result to manufacture further
caverns have different specifiable atmospheric pressures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 shows the preparation of a substrate and of a
glass.
[0023] FIG. 2 shows the joining of the substrate and glass by
anodic bonding.
[0024] FIG. 3 shows the thinning of the glass layer.
[0025] FIG. 4 shows the etching of recesses into the glass.
[0026] FIG. 5 shows the application of a shield and parallelizing
of the substrate.
[0027] FIG. 6 shows the alignment of a cap with respect to a
micromechanical component.
[0028] FIG. 7 shows the joining of the component and cap.
[0029] FIG. 8 shows the production of an access opening to a
cavern.
[0030] FIG. 9 shows the closing off of the access opening.
[0031] FIG. 10 shows the production of a back-side contact.
[0032] FIG. 11 shows an assemblage of multiple caverns in one
micromechanical component.
DETAILED DESCRIPTION
[0033] FIG. 1 shows the preparation of a substrate and a glass for
the manufacture of a cap. A cap substrate 100, which in this
example is made of silicon, is disposed and aligned with respect to
a glass 150. Glass 150 is made of Pyrex in this example. For
joining, cap substrate 100 and glass 150 must exhibit a suitable
roughness on the surfaces facing one another.
[0034] FIG. 2 shows the joining of substrate 100 to glass 150. The
joining is accomplished, for example, by way of the technique of
anodic bonding.
[0035] FIG. 3 shows the thinning of the glass layer. Thinning
action 300 of glass 150 is accomplished by grinding and
chemical-mechanical polishing (CMP). The result is to produce, in
this example, a glass layer 150 having a thickness of approx. 50
.mu.m.
[0036] FIG. 4 shows the production of recesses in the glass.
Recesses 400 in glass 150 can be produced, for example, by a
buffered oxide etch (BOE) method. In the example shown, recesses
400 have a depth of approx. 5.5 .mu.m. Provision can be made to
leave supporting regions 450 when producing the recesses.
[0037] FIG. 5 shows the production of a shield and the
parallelizing of the cap substrate. To produce a shield 550, a
metal layer is deposited onto regions of glass layer 150, in
particular in the region of recesses 400 and support region 450.
This metal layer can be made, for example, of aluminum, and here
has a thickness of approx. 400 nm. The metal layer can be
deposited, if necessary, in structured fashion, or can also be
structured after deposition. Shield 550 can optionally have a
contact tab 555, such that a conductive connection can be contacted
thereon.
[0038] In the next manufacturing step, cap substrate 100 is
parallelized. Parallelizing action 560 is accomplished from the
back side of cap substrate 100. The purpose of parallelizing action
560 is to ensure that the substantially disk-shaped cap substrate
100 has approximately the same thickness (approx. 450 Am in this
example) everywhere. Cap substrate 100, glass layer 150, and shield
550 together form a cap 500.
[0039] FIG. 6 shows the alignment of the cap with respect to a
micromechanical component. Micromechanical component 600 has a
micromechanical functional layer 610 made of polycrystalline
silicon, a dielectric layer 620 made of silicon oxide, and a
component substrate 630 made of silicon. Micromechanical functional
layer 610 has a connection region 640, micromechanical structures
650, and optionally support mounts 655. On the surface facing
toward micromechanical component 600, glass layer 150 in cap 500
has bonding surfaces 660.
[0040] FIG. 7 shows the joining of component and cap., in which cap
500 is anodically bonded to component 600 at bonding surfaces 660.
This material join of glass layer 150 to micromechanical functional
layer 610 is hermetically sealed. As a result, cap 500 and
micromechanical component 600 delimit at least one cavern 700.
[0041] FIG. 8 shows the production of an access opening to a
cavern. Firstly, a thinning action 800 of component substrate 630
to a thickness of approx. 125 .mu.m occurs. Thinning action 800 is
performed, for example, by grinding and polishing. Trenches 810
that isolate contact regions 830 from the remaining component
substrate 630 are then introduced into component substrate 630. In
the same manufacturing step, an access opening 820 to cavern 700 is
introduced into component substrate 630. The internal atmospheric
cavern pressure is equalized with the ambient pressure through
access opening 820.
[0042] FIG. 9 shows the closing off of the access opening. For
this, component substrate 630 is coated with an oxide 900; this is
done, for example, using a CVD method. Oxide 900 fills insulating
trenches 810, closes off access opening 820, and furthermore coats
component substrate 630. The process pressure during coating, which
can be less than 10.sup.-3 bar, is thereby enclosed in cavern 700.
Contact region 830 is at least partially exempted from the coating
with oxide 900.
[0043] FIG. 10 shows the production of a back-side contact on
micromechanical component 600, a metallization 10 being applied
onto contact region 830 and locally onto oxide 900. Metallization
10 can be structured during application, or also in a later
manufacturing step. Contacts to conductive regions in the interior
of the micromechanical component, as well as contacts and
conductive paths on the surface, can be produced by way of this
process step.
[0044] FIG. 11 shows a micromechanical component according to the
present invention having multiple caverns. The component is
depicted schematically and in plan view. Caverns 700a, b are
located in the interior of the micromechanical component, and in
this example are formed by a single common cap on the component.
The cap and component have joining surfaces 660 that, in this
example, form a first bonding frame 113 and a second bonding frame
115 after anodic bonding. First bonding frame 113 encloses a cavern
700a that has a closed-off access opening 820. A very low internal
atmospheric pressure exists in this cavern 700a; an internal
pressure of less than 10.sup.-3 bar is conceivable. Cavern 700a
accommodates a micromechanical functional element 111 that
operates, as governed by its design, at very low pressures. This
can be, for example, a micromechanical rotation-rate sensor or
another high-quality micromechanical oscillator. The vacuum in
cavern 700a is hermetically closed off from ambient pressure by
bonding frame 113.
[0045] In this example, the micromechanical component has three
further caverns 700b that have no access opening 820 at all. These
caverns 700b contain substantially the process pressure that
existed during the process step of anodic bonding. These can be,
for example, pressures between 5 mbar and 1.5 bar. Disposed in
these caverns 700b are functional elements 110 that, as governed by
their design, function at higher pressures or are more tolerant to
higher working pressures. Micromechanical functional elements 110
can be, for example, acceleration sensor structures that operate in
damped fashion at the indicated internal atmospheric pressure of
caverns 700b.
[0046] The three caverns 700b having the higher internal pressure
are hermetically closed off by bonding frame 113 from the vacuum in
fourth cavern 700a. Furthermore, all the caverns 700a, b are
hermetically closed off from the outside world by the common
bonding frame 115. In this example, the three caverns 700b having
the higher internal pressure are not separated from one another by
further bonding frames, since substantially the same internal
cavern pressure exists in them in any case after the process step
of anodic bonding.
[0047] Lastly, FIG. 11 also depicts contact surfaces 10 produced by
metallization. By way of these contact surfaces, the
micromechanical component can, for example, be connected to an
external evaluation circuit (not depicted here). It is also
conceivable, however, to integrate the evaluation circuit into the
micromechanical component.
[0048] Further embodiments of the micromechanical component are
possible.
* * * * *